Fire test results support mass timber high-rise construction

Framework—a 12-story wood building to be constructed in Portland’s Pearl District—will be the first high-rise with exposed wood in North America. Images courtesy The Framework Project LLC
Framework—a 12-story wood building to be constructed in Portland’s Pearl District—will be the first high-rise with exposed wood in North America.
Images courtesy The Framework Project LLC

The Framework Project LLC has completed two significant fire tests on cross-laminated timber (CLT). These tests were intended to answer a number of questions relating to mass timber high-rise construction—namely, whether CLT and glued-laminated timber (glulam) are viable as building materials that meet fire code requirements.

Project-specific tests for beam exterior column connections, cross-laminated timber (CLT) deck-to-beam connection, penetrations fire resistance, and wall fire resistance were conducted at a Texas facility.
Project-specific tests for beam exterior column connections, cross-laminated timber (CLT) deck-to-beam connection, penetrations fire resistance, and wall fire resistance were conducted at a Texas facility.

Testing was done on both local Oregon CLT and non-local material, to ensure usable wood could be obtained from both sources. The tests were funded by a $1.5 million grant from the U.S. Department of Agriculture (USDA), Softwood Lumber Board, and Binational Softwood Lumber Council, provided as part of the 2014 U.S. Tall Wood Building Prize Competition. (Framework was the West Coast winner of this competition.)

As a condition of this grant, all the project’s test results will be made public, from the fire tests already completed to the structural tests currently underway (to be completed in November). According to the organizers, the intent is to alleviate the need for teams working on similar projects to conduct testing of their own.

Tests completed and still in progress are as follows:

  • project-specific tests to ensure Oregon Structural Specialty Code (OSSC) fire rating requirement compliance, including a beam-exterior column connection test, CLT deck to beam test, penetrations fire resistance rating test, and wall fire resistance rating test (conducted July to November at a facility in Texas);
  • CLT wall panel tests for the panels’ basic in-plane structural stiffness properties, including regular CLT wall panel tests and CLT wall panel tests with cruciform connector splice tests, with epoxied rod splice tests, and with HSK system splice tests (conducted September to November at Oregon State University);
  • CLT crushing tests to determine the project’s structural properties when exposed to stress and strain, including regular CLT wall panel tests and CLT wall panel tests with reinforcing screws tests and with steel guard plate tests (conducted September to November at Oregon State University);
  • floor assembly acoustic tests to gauge the acoustic performance of the project’s floor assembly, including a sound transmission test and impact transmission test (conducted in October by Intertek); and
  • a glulam beam-column connection test to determine how well the connection performs under load and imposed seismic drifts (conducted October to November at Portland State University).
A view of the column-to-beam connection prior to fire testing.
A view of the column-to-beam connection prior to fire testing.

Results for the completed fire tests found CLT panels fully complied with building code flame spread and fire rating requirements, while the glulam beam-to-column connection’s two-hour fire rating exceeded any results worldwide. The same rating holds true for CLT floors. This means mass timber can indeed be used to construct high-rise buildings with some timber exposed.

This is good news for the team working on Framework, which will be a 12-story wood building located in Portland’s Pearl District. The building—designed by Lever Architecture and developed by project^—makes groundbreaking use of both CLT and glulam. It will be the first high-rise with exposed wood in North America and both the first and tallest mass timber high-rise in the United States, with the first fully-loaded exposed CLT and glulam connections to require a two-hour fire rating in the world. It is also the first North American project to carry out fire tests on these connections, CLT, and glulam beam-floor assembly.

“Framework…can serve as a national case study toward a more sustainable future and a beautiful building material and technology,” said Anyeley Hallóva, a developer for project^.

The project’s design was approved by the City of Portland in July. Construction should begin in March, and conclude one year later.

The results of these tests imply timber high-rise construction is code compliant and feasible.
The results of these tests imply timber high-rise construction is code compliant and feasible.
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